Clutches within planetary transmissions tie two rotating components together or to a ground member, such as a transmission housing. By engaging various clutches, different gear ratios can be obtained. When the clutch is engaged a reactive torque is transmitted to the case.
U.S. Pat. No. 5,724,865 to F. Michael Boone discloses a caseless planetary transmission, which includes an integrated clutch/clutch housing. Stacking the clutch housings together creates a case. Bolts are used to tie the integrated clutch housings together so that one integrated clutch housing does not slip with respect to the other. The bolts must be long enough to pass through each of the integrated clutch housings and into the transmission housing. Due to the length of the bolts and extreme torque conditions, the bolts must be high quality. Accordingly, the bolts are expensive. Similarly, the bolts are heavy, require bolt dampers, and require precise engagement, which increases the price and weight of the transmission.
Other transmissions couple the clutch assemblies to the transmission housing through a series of clutch teeth that protrude into the transmission housing. Advantageously, torque is directly transmitted into the housing. For large transmissions having multiple planetary gear sets, casting deep sets of clutch teeth has been prohibitively expensive.
Current high production casting technology is limited to a predetermined cast depth. In other words, the tolerances of the cast product may be too great if the cast is too deep. For transmission castings, the draft is generally between one and five degrees, which may result in unacceptably long clutch teeth if the cast is too deep.
U.S. Pat. No. 1,472,104 to A. B. Browne attempts to overcome this deficiency by bolting the gear teeth to the transmission housing. Unfortunately, the torques acting on the transmission housing react across the bolted joint.
The present invention is directed to overcoming one or more of the problems identified above.